When Geoffrey Hosking was given the chair of Russian history at London University 17 years ago, he was one of a tiny group of Britons who had spent time in the country he taught about. Travel by foreigners outside a few tourist centres was difficult; at one point in the 1980s, the Soviet Foreign Ministry produced a map showing which parts of the USSR were closed to visitors. Almost all of it was.

Then, foreign academics and students were permitted short, circumscribed stays in parts of the Soviet Union. Diplomats and journalists lived there on condition they paid huge amounts of money for what was, in effect, the cost of spying on themselves, given that they were obliged to hire a retinue of (assumedly KGB) servants. This made the life of Sovietologists like Hosking difficult, but it also gave what hard-won personal knowledge they had gained of the country great weight, since it was such a precious commodity in the West.

All that has changed. The boutique of Soviet glimpses has become the retail warehouse of post-Soviet memoirs and travelogues - and quantity has not harmed quality, since many are very good. The established Western historians of the Soviet era, accustomed to reading about places and people rather than being able to go to them, found themselves in competition with eloquent young unknowns combining a knowledge of history with a journalistic sensibility and the opportunity to go wherever they liked.

Some Sovietologists, particularly in the US, went into denial, continuing to treat Russia as if it was the USSR, a remote menace, knowable by its steel-production statistics, reported speeches of its leaders and the occasional Moscow seminar. Hosking is different. Having written one of the authoritative histories of the Soviet Union in the 1980s, he has taken the new order in Eurasia as the opportunity to fold that 74-year history into the 1,000-year history of Russia. Rather than heading off to the post-Soviet hinterland, he has played to his strength, a lifetime of scholarship.

Don Corleone's speech to the supplicant at his daughter's wedding in The Godfather would be a good taster for the theme Hosking convincingly picks out from the early days of Kievan Rus to the present: protection. It is to Corleone that the undertaker comes seeking justice when the law, the rules by which Western societies live, fails him. The search for personal protection as a substitute for non-existent or derelict laws, and the moral corruption which comes with being a personal protector, has been a universal experience of Russians. Instead of a civic society, Russia was and remains a network of what Hosking calls patron-client networks. The patron/protector might be a boyar, a tsar, a president, a minister, a businessman, a criminal or abbot; the effect is the same, to undermine what fragile national institutions or laws exist on paper.

One of Russia's tragedies is that its rulers have often understood this, that it would be better to devolve power to representative institutions, assemblies and judges, rather than to individuals. But they have always drawn back, terrified of the vastness of their country, the volatile passions of its people, and the difficulty of defending its borders without tight personal control; under pressure from patrons and protectors who do not want to lose privileges; and repeatedly convinced, against all lessons of history, that absolute monarchies or dictatorships can ram through radical reforms without reforming themselves.

Sifting the sixteenth-century tsar Ivan the Terrible's bloody insanity from his statecraft, Hosking accuses him of 'inaugurating a tradition that in order to unite and mobilise, Russian rulers had to be harsh and overbearing, even to violate God's law, to the extent of risking disunity and demoralisation, and of undermining the ideals which the monarchy itself professed... thus was launched the peculiarly Russian style of governance: a huge, diverse and vulnerable empire resting on personal powerbroking'.

It is no exaggeration to say that this tradition is still endorsed by Russia's gosudarstvenniki, influential 'strong-stateists' who have Vladimir Putin's ear; and that five centuries after Ivan Russia still rests on personal powerbroking. Whether it is still an imperial power is disputable. Western writers have often yielded to the temptation to treat post-1991 Russia as if, geopolitically, it was an altered Soviet Union or Russian empire. In fact, it has barely half the population of the USSR.

The implication of Hosking's history is that this should be an opportunity for Russia to become a nation at last, an aim which was in the past always sacrificed to a strange form of imperialism, whereby no matter how large the empire grew a small group of Russians treated the remainder as a subject people. There has always been an ambiguity about slavery and individual status in Russia. Russian serfs were simultaneously subject to brutal control over their lives and lauded by the élite as the guardians of Russian values, while in the labour camps of the Stalin era, the slaves could always think of themselves as victims of miscarriages of justice, yet their immediate masters were as likely to be taken out and shot as they were.

Hosking has some brilliant insights into the strangest chapters of Russia's past, such as the sundering of the Westernised nobility from Orthodox traditions in the eighteenth century, and the birth of organised anti-Semitism some hundred years later. 'It was a projection on to Jews of the embitterment many Russian intellectuals experienced at not being able to bring Russian nationhood to full flowering: they felt they were being internally undermined by some mysterious alien and international force,' writes Hosking. 'In a sense they were right, but the real culprit was the Russian state, which had imported an alien culture and outlawed the original Russian national myth.'

There is much of Russia and the Russians which is recording, a recitation of events where Hosking pauses to analyse but seldom stops to delve into the pain or joy of a moment for those involved. That said, to enter Russia's most ancient past and march out at the other end with one's thoughts in good order is a Napoleonic ambition, one which Hosking has fulfilled.